Osteoporosis, boron, prunes and bones

June 8, 2011

Prunes for osteoporosis? Yes, that’s right, osteoporosis. Prunes are justifiably famous, or perhaps I should say infamous, for another condition. But prunes are a versatile fruit, and they are also good for your bones. Prunes, or to be politically correct here, dried plums, have been found to prevent and reverse bone loss in two animal studies. In one of these, published in 2001, dried plums prevented bone loss in rats whose ovaries had been removed. In another study, published in 1999, dried plums were able to reverse bone loss in rats whose ovaries had been removed and who were in the early stages of osteoporosis.

In a human study published in 2002, dried plum supplementation for three months significantly increased biochemical markers of bone formation in postmenopausal women. These findings suggested that dried plums have the ability to increase bone formation in postmenopausal women, thus decreasing the risk of osteoporotic fractures. A logical question is what component of dried plums exerts the beneficial effects on bone? Although the question has not yet been answered, dried plums are known to be an important source of boron, and boron is known to play a role in the prevention of osteoporosis.

The discovery of boron’s effect on bones

The role of boron in nutrition was accidentally discovered by two researchers, Dr. F. H. Nielsen and Dr. C. D. Hunt, in the course of another investigation. They were trying to ascertain the role of arsenic in nutrition when the chicks they were studying developed growth problems and leg abnormalities. The researchers found that the lack of a previously unrecognized nutrient, boron, caused the problem. When boron was added to the chicks’ diet, their bones developed normally as long as other factors crucial to bone growth, such as vitamin D, were also present.

Motivated by this discovery, Nielsen and Hunt studied the effect of boron on bone loss in postmenopausal women. In a study published in 1987, they studied 12 postmenopausal women for six months. The women lived in a nutrition center for these six months and received all their food only from the center. This way the researchers were able to control completely what the participants ate. For the first four months, the women were maintained on a low boron diet of one-fourth of a milligram of boron per day. This reduction in boron intake was accomplished by restricting fruits, vegetables and nuts, the main dietary sources of boron. Boron deprivation increased the urinary excretion of calcium and magnesium, two minerals crucial to the formation of new bone, and decreased estrogen concentrations in these postmenopausal women.

How boron protects bones

After 119 days, an additional 3 milligrams of boron were provided in supplement form. The extra supply of boron produced some remarkable results in the body’s metabolism. First, boron supplementation reduced the urinary excretion of calcium and magnesium, allowing more of these minerals to remain in the body to form new bone. Second, boron increased concentrations of the sex hormones estrogen and testosterone in the blood. In fact, estrogen levels rose to those typically found in postmenopausal women on estrogen replacement therapy.

In another study by Nielsen, published in 1989, supplementation of a low boron diet with 3 milligrams of boron per day increased blood levels of the biologically active hormonal form of vitamin D. These studies found that boron has a powerful influence on calcium, magnesium, estrogen, testosterone and vitamin D - each of which plays a role in the prevention of bone loss.

Where boron is found

Diets containing a variety of foods including fruits and vegetables should supply about 1.5-3.0 milligrams of boron per day. The RDA for boron has not been established. Dietary requirement is estimated at approximately 1 milligram per day and up to a safe dietary limit of approximately 10 milligrams per day. Boron is toxic in excess amounts. The best way to increase boron intake is through the diet by eating foods in which it is found. These are fruits, legumes, nuts and vegetables in the cabbage family. Among foods known to be especially good sources are apples, grapes, pears, cherries and, of course, prunes - oops, I mean dried plums.

Mary Lou Williams, M. Ed., is a writer and lecturer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.